The prior art syringes usually include pushbutton valves to control the flow of streams of compressed air and water to a nozzle which is mounted on one end of the instrument, the valves being sealed by O-rings. Apart from being complex and expensive, the prior art syringes have a tendency to stick due to debris and/or droppage. The syringe of the present invention on the other hand, which uses pinch valves, is rugged in its construction, simple in its operation, inexpensive and uncomplicated, and it has no tendency to stick, even when subjected to rough usage. Moreover, the syringe of the present invention is reliable in operation, and its life span can be extended merely by moving the tubing therein slightly to produce new pinch points when the previous pinch points show signs of wear, this being achieved without any need to disassemble the instrument or to provide new parts.
It will be evident as the description proceeds that although the pinch valves used in the instrument to be described are particularly suited to enable the instrument to perform a syringe function, the pinch valves may be used in other applications wherever a particular fluid flow control through one or more flexible tubes is desired.